Anode potential selection for sulfide removal in contaminated marine sediments

Sulfate reducing microorganisms are typically involved in hydrocarbon biodegradation in the sea sediment, with their metabolism resulting in the by-production of toxic sulfide. In this context, it is of utmost importance identifying the optimal value for anodic potential which ensures efficient toxic sulfide removal. Along this line, in this study the (bio)electrochemical removal of sulfide was tested at anodic potentials of −205 mV, +195 mV and +300 mV (vs Ag/AgCl), also in the presence of a pure culture of the sulfur-oxidizing bacterium Desulfobulbus propionicus. Current production, sulfide concentration and sulfate concentration were monitored over time. At the end of the experiment sulfur deposition on the electrodes and the microbial communities were characterized by SEM-EDS and by next generation sequencing of the 16S rRNA gene respectively. Results confirmed that current production was linked to sulfide removal and D. propionicus promoted back oxidation of deposited sulfur to sulfate. The highest electron recovery was observed at +195 mV vs Ag/AgCl, and the lowest sulfur deposition was obtained at −205 mV vs Ag/AgCl anode polarization.